A new book claims smoking, drinking or stress during pregnancy can affect a child's sexual orientation.

According to the UK Daily Mail, Dutch neuroscientist Dick Swaab writes in his book We Are Our Brains: “Although it's frequently assumed that development after birth also importantly affects our sexual orientation, there's no proof of this whatsoever.”

“Children brought up by lesbians aren't more likely to be homosexual. Nor is there any evidence at all for the misconception that homosexuality is a 'lifestyle choice.'”

Swaab, who is based at the University of Amsterdam, claims that the lifestyle of expectant mothers affects the sexuality of their unborn baby. Factors Swaab cites include smoking, taking drugs or stress during pregnancy.

“Pregnant women suffering stress are also more likely to give birth to homosexual children, because their raised levels of the stress hormone cortisol affects the production of fetal sex hormones,” Swaab wrote.